1. Field of the Invention
This invention relates to toughened cyanoacrylate compositions which exhibit improved peel strengths and fixture speeds. The toughening agent used in the present invention comprises poly(vinychloride-co-vinyl acetate) in combination with poly(methylmethacrytlate).
2. Brief Description of Related Technology
Cyanoacrylate compositions are well known as one component reactive adhesives, quick bonding and suitable for a variety of substrates. However, traditional cyanoacrylate-based adhesives tend to be brittle, and to have low peel strengths. A variety of additives and fillers have been proposed for addition to cyanoacrylate adhesive compositions to improve toughness and peel strengths.
U.S. Pat. No. 4,102,945 (Gleave) describes a cyanoacrylate adhesive having enhanced peel strengths in which a cyanoacrylate is thickened by a copolymer or terpolymer including vinylidene chloride-acrylonitrile copolymers.
U.S. Pat. No. 4,440,910 (O'Connor) is directed to cyanoacrylate compositions having improved toughness, achieved through the addition of elastomers, i.e., acrylic rubbers. These rubbers are either (i) homopolymers of alkyl esters of acrylic acid; (ii) copolymers of another polymerizable monomer, such as lower alkenes, with an alkyl ester of acrylic acid or with an alkoxy ester of acrylic acid; (iii) copolymers of alkyl esters of acrylic acid; (iv) copolymers of alkoxy esters of acrylic acid; and (v) mixtures thereof.
U.S. Pat. No. 4,444,933 (Columbus) suggests the addition of a vinyl chloride/vinyl acetate copolymer to a cyanoacrylate adhesive to reduce adhesion to human skin.
U.S. Pat. No. 4,560,723 (Millet) discloses a cyanoacrylate adhesive composition containing a toughening agent comprising a core-shell polymer and a sustainer comprising an organic compound containing one or more unsubstituted or substituted aryl groups. The sustainer is reported to improve retention of toughness after heat aging of cured bonds of the adhesive.
U.S. Pat. No. 4,713,405 (Koga) discloses an α-cyanoacrylate adhesive composition of matter consisting essentially of α-cyanoacrylate, fumed silica having a surface treated with a dimethyldichlorosilane, and trialkyl borate.
U.S. Pat. No. 5,340,873 (Mitry) discloses a cyanoacrylate adhesive composition having improved toughness by including an effective toughening amount of a polyester polymer derived from a dibasic aliphatic or aromatic carboxylic acid and a glycol.
U.S. Pat. No. 5,739,205 (Nishino) discloses an α-cyanoacrylate adhesive composition which comprises (a) 100 parts by weight of an α-cyanoacrylate compound, (b) 10 through 20 parts by weight of (I) polyalkyl methacrylates having a weight average molecular weight of 100,000 through 300,000, or (II) copolymers of alkyl methacrylates and other methacrylates or acrylates, said copolymers having the same weight average molecular weight as that of the polyalkyl methacrylates (I), (c) 2 through 20 parts by weight of ultrafine anhydrous silicas, and (d) 0.001 through 20 parts by weight of certain quick curing additives, (b)-(d) being on the basis of (a) 100 parts by weight of α-cyanoacrylate compounds.
U.S. Pat. No. 5,994,464 (Oheawa) discloses a cyanoacrylate adhesive composition containing a cyanoacrylate monomer, an elastomer miscible or compatible with the cyanoacrylate monomer, and a core-shell polymers being compatible, but not miscible, with the cyanoacrylate monomer.
U.S. Pat. No. 6,475,331 (O'Connor) discloses and claims a cyanoacrylate adhesive composition comprising: (a) a cyanoacrylate components; and (b) an accelerator component consisting essentially of (i) calixarenes, oxacalixarenes, or a combination thereof, and (ii) at least one crown ether, wherein said composition exhibits a fixturing speed of less than 20 seconds for bonding two substrates, at least one of which is constructed of a material selected from steel, epoxy glass, and balsawood.
Despite the state of the technology, there continues to be a need for cyanoacrylate adhesives with improved toughness and peel strengths, while maintaining a high fixture speed.